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I’d like to share two thoughts with you all. They involve the RCX and doing
things with it that I’m sure the designers never intended (or thought possible).
Oh, if you’re reading this in the .trains newsgroup, you can skip over the first
thought because it doesn’t involve trains. But the second one does.
1.
Last year I was thinking about the fact that the motor outputs send pulses of
current. So, I was wondering if the input ports were polled fast enough to
sense this. The idea was you could hook up a motor output from one RCX to an
input port of a second RCX, creating a physical link between them for
communication. This would be advantagous in situations where the two RCXs’ IR
ports can’t “see” each other.
I took my RCX to the electronics lab at school and hooked it up to an
oscilloscope. I really wish I had written down what my professor and I saw, but
the pulses were very fast; I believe they were 20ms each. If that number is
incorrect, it’s due to my failing memory, but I know for sure they were in the
millisecond range. I also remember that the pulse that’s on for 7 ticks and off
for 1 didn’t look much different than the pulse that’s on for the full 8 ticks.
Anyway, I don’t think the input ports can sense stuff that fast, so that was my
first question for you all: How often are the input ports polled?
I wasn’t a LUGNET member back then, otherwise I would have asked this sooner.
Oh yeah, one other thing. I’m not sure how much voltage or current the inputs
can handle. There might have to be some kind of load in between the two RCXs. I
was thinking of using a bunch of 9V lights connected in series (that’s actually
hard to do -- try it sometime.)
2.
The second idea came to me yesterday as I was reading
this thread. I wondered if
instead of building a contraption involving magnets and a light sensor, could I
instead simply induce current in a wire as a LEGO train and its coupling magnets
passed above it? That would tell the RCX the train passed that point.
The answer was no. I put the end of a LEGO wire on a baseplate between two 9V
track ties (in between the rails, too). Then I attached a multimeter to the
other end. I waved my LEGO magnets over the end in the track, but no current. I
drove a train car with its magnets over it, and still no current. Hmmmm.
I then put a 2x4 electric plate on top of the wire’s end, thinking that a larger
area would work. Nope, it didn’t.
Neither did a 2x8 electric plate.
It’s been a long while since I took physics, so I think I need a coil of wire,
not just a wire/electric plate. And a much bigger magnet.
Oh well. Thanks for reading.
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Message has 5 Replies:
 | | Re: Weird RCX electrical ideas
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| (...) Voltage shouldn't be much of a concern, unless the RCX has a transformer to allow it to output higher voltage than the internal batteries can provide. Besides, wiring up a bunch of 9v lights will increase the total voltage needed to make them (...) (21 years ago, 1-Sep-03, to lugnet.robotics, FTX)
| | | Re: Weird RCX electrical ideas
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| <snip> (...) Well Jordan I know a little about DC motor theory. In essence a DC Motor and a DC Generator are the same thing. The amount of ripple (i.e. the frequency of the pulses although frequency is a bad term to use) is dependent on 2 things: (...) (21 years ago, 1-Sep-03, to lugnet.robotics)
| | | Re: Weird RCX electrical ideas
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| (...) A much simpler "contraption" that you can build is discussed in (URL) this LUGNET message>. The basic idea is that you place a reed switch in the railbed and it will sense the magnetic couplers between the cars of passing trains. I have been (...) (21 years ago, 1-Sep-03, to lugnet.robotics, FTX)
| | | Re: Weird RCX electrical ideas
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| (...) Although these pictures come from as imulator, they are quiet like you probably have seen on the scope, see .. (URL) this page might be of interest, describing both sensor and motor terminals: (URL) Mientki (21 years ago, 5-Sep-03, to lugnet.robotics)
| | | Re: Weird RCX electrical ideas
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| I certainly don't see a reason why the whole motor-to-sensor thing wouldn't work. Actually, it's really a good idea, I don't know how much has been done with it before, but it sounds like it could be a great little serial interface - if programmed (...) (21 years ago, 15-Sep-03, to lugnet.robotics)
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